In the course of the night calm has returned to Munich, police chief Hubertus Andrä confirmed. He said that 550 police were involved in the investigation of what he confimed was a warning of a suicide attack.

A police spokesperson had confirmed to media earlier that there had been "two concrete tips" of planned attacks with an "Islamist background."

On Thursday evening Munich police warned via Twitter of a possible terror attack: "Please avoid large crowds and the main train station and the one in Pasing" they published via twitter:

The two affected stations were reopened several hours later.

The interior minister of the state of Bavaria, Joachim Herrmann, revealed that a foreign security service had passed on the information on New Year's Eve. He confirmed that the threat had been linked to the "Islamic State" terrorist movement.

He said that the tips had specifically referred to the two train stations and that attacks were planned for midnight.

The Munich daily newspaper Süddeutsche Zeitung reported that six suspects were the target of the investigation.

rg/bik (AFP, dpa, Reuters)